Day 26: Using time.sleep() in Async Code

 

🐍 Python Mistakes Everyone Makes ❌

Day 26: Using time.sleep() in Async Code

Async code is powerful—but one small mistake can completely block it.

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❌ The Mistake

import time

async def task():
    print("Start")
    time.sleep(2) 
    print("End")

Looks harmless, right?
But this breaks async behavior.

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🤔 Why This Is a Problem

• time.sleep() blocks the entire event loop

• No other async tasks can run during the sleep

• Your “async” code becomes sync and slow

In async code, blocking = 🚫 performance.

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✅ The Correct Way

Use asyncio.sleep() instead:

import asyncio

async def task():
    print("Start")
    await asyncio.sleep(2) 
    print("End")

This pauses without blocking, allowing other tasks to run.

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❌ Why the Mistake Is Dangerous

• Freezes concurrent tasks

• Ruins scalability

• Causes confusing performance issues

• Defeats the purpose of async programming

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🧠 Simple Rule to Remember

✔ Never use time.sleep() in async code
✔ Always use await asyncio.sleep()
✔ Blocking calls don’t belong in async functions

🐍 Async rule: If it blocks, it doesn’t belong in async def.